The celebrated art historian and critic, Berenson, was equally known for his connoisseurship. His expertise in this area resulted in the acquisition of some superb works of art for American collectors and dealers, among them Isabella Stewart Gardner and Joseph Duveen.

If we feel the identical sense of form, the identical tendencies in visualizing and executing, the identical vibration of vitality or touch that we call quality, we conclude for ourselves, and for the like-minded only, that the drawing is by the same hand that created the series of works that constitute a given artistic personality. This is scarcely the answer that will satisfy the collector Jacob and his brother the dealer Esau, but disinterested students should know that no other answer is permissible….

To the question of how we know that a drawing is by a given master, an honest answer should begin by confessing that our knowledge is never strictly scientific… but it is at best only plausible. There is only one way of reaching even this plausibility, and that is through the feeling a drawing gives us that it was created by the same spirit that we find in a series of paintings or sculptures well known to us… I should like to add a word about quality. In our studies it is not enough to have the abstract sense of it. We must learn to recognize precisely how it is conditioned in each individual draughtsman by the idiosyncrasies of his temperament, his training, his circumstances and his momentary mood…